Westmorland Green roofing slate is from the Borrowdale Volcanic Group of mountains in the Lake District and was formed 500 million years ago during the Ordovician period by the metamorphosis of sedimentary layers of volcanic ash.
This unique geology makes the slate unrivalled in terms of quality. It is unlike any other roofing slate in the world and its metamorphic volcanic ash composition means it lasts for many hundreds of years. This is evidenced by empirical observation, where we see roof timbers and building structures fail, but Westmorland green slate is capable of being stripped, re-dressed and used time and time again.
This unparalleled durability, aligned with the slates attractive green colour, made it the obvious choice historically for architects building important public and ecclesiastical buildings where it was necessary for the client to make a statement of quality and permanence. As such, it is very common to see these important buildings, the Town Halls, Churches, School Houses, Police Stations, Libraries, Museums, etc., in every village, town and city across the UK, slated with Westmorland green slates.
The Westmorland green quarries produced random sized block (‘clog’) and in order to make best use of this varied shaped raw material, Westmorland green slates were almost always produced in random sizes for laying in diminishing courses, and it is extremely unusual to come across the material is set sizes.
Today Westmorland green slates are produced in the same traditional random format for laying in characterful diminishing courses.